Method and apparatus for allocating flexible transmission slot in wireless LAN system

ABSTRACT

A method and an apparatus for allocating a flexible transmission slot in a wireless local area network (LAN) system are disclosed. A flexible transmission slot allocation method of an access point (AP) in a wireless local area network (WLAN) system according to an exemplary embodiment includes transmitting a beacon including a traffic indication map (TIM) bit to a station, receiving a power save poll (PS-Poll) from the station in a slot implicitly allocated by the TIM bit, and transmitting an acknowledgement (ACK) including transmission slot allocation information on downlink data to the station.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.application Ser. No. 14/414,087, filed Jan. 9, 2015, which is a NationalPhase of International Application No. PCT/KR2013/006154, which claimspriority to Korean Application Nos. 10-2013-0080846, filed Jul. 10,2013, 10-2012-0109698, filed Oct. 2, 2012, 10-2012-0075287, filed Jul.10, 2012, the contents of which are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a method and an apparatus forallocating a flexible transmission slot in a wireless local area network(LAN) system.

BACKGROUND ART

Wireless local area network (LAN) technology is advancing in threedirections.

First, a 60-GHz band and a 5-GHz band are used in a wireless LAN inorder to enhance a transfer rate. Second, a frequency band of less than1 GHz is used for a wideband wireless LAN uses to expand a coveragethereof as compared with conventional wireless LAN technology. Third, atechnique of reducing a link setup time of a WLAN system is adopted. Awideband wireless LAN is required to accommodate a remarkably largernumber of stations (STAs) than an established wireless LAN.

A slot-based channel access mode may be used in a wireless LAN system.To make the slot-based channel access mode available, transmission slotallocation is needed for STAs.

In allocation of transmission slots, variable slots may be allocated forSTAs within each restricted access window (RAW) to efficiently manageslots. However, amount of transmission information for transmitting slotallocation information may increase too much in each RAW

For instance, since information on the RAW is included in a short beaconin transmission, the beacon becomes too large.

Further, when the transmission slot allocation information istransmitted in a separate frame, instead of the beacon, overhead oftransmitting the frame occurs. Also, an STA operating in power sleepmode may have overhead of waking up to receive the frame.

When fixed transmission slots are allocated for STAs to reduce the slotallocation information in the RAW, signaling may become simple but slotmanagement lacks flexibility.

DISCLOSURE OF INVENTION Technical Goals

To overcome problems of the conventional technology, an aspect of thepresent invention is to provide a method and an apparatus for preventingwaste of slot time and efficiently managing transmission slots byreducing overhead in transmission slot allocation and enabling flexibleslot allocation.

Further, an aspect of the present invention is to provide a method andan apparatus for allocating temporary slots when transmission slots areinsufficient for downlink and uplink transmission in a wireless LANsystem.

Technical Solutions

A flexible transmission slot allocation method of an access point (AP)in a wireless local area network (LAN) system according to an exemplaryembodiment includes transmitting a beacon including a traffic indicationmap (TIM) bit to a station, receiving a power save poll (PS-Poll) fromthe station in a slot implicitly allocated by the TIM bit, andtransmitting an acknowledgement (ACK) including transmission slotallocation information on downlink data to the station.

A flexible transmission slot allocation method of a station in awireless LAN system according to an exemplary embodiment includesreceiving a beacon including a TIM bit from an AP, transmitting aPS-Poll to the AP in a slot implicitly allocated by the TIM bit, andreceiving an ACK including transmission slot allocation information ondownlink data from the AP.

A flexible transmission slot allocation method of a station in awireless LAN system according to another exemplary embodiment includesverifying information on a restricted access window (RAW) included in abeacon or information on a slot regularly allocated at association,transmitting uplink data to an AP in an uplink slot, and receiving anACK from the AP, wherein the uplink slot includes a fixed size of slotduration.

A flexible transmission slot allocation method of an AP in a wirelessLAN system according to another exemplary embodiment includestransmitting a beacon including information on an RAW to a station,receiving uplink data in an uplink slot allocated to the station basedon the information on the RAW or regularly allocated to the station atassociation, and transmitting an ACK with respect to the uplink data tothe station, wherein the uplink slot includes a fixed size of slotduration.

An AP of a wireless LAN system according to an exemplary embodimentincludes a transmission unit to transmit a beacon including a TIM bit toa station, a reception unit to receive a PS-Poll from the station in aslot implicitly allocated by the TIM bit, and a controller to controlthe transmission unit to transmit an ACK including transmission slotallocation information on downlink data to the station and to controlslot allocation.

An AP of a wireless LAN system according to another exemplary embodimentincludes a transmission unit to transmit a beacon including informationon an RAW to a station, a reception unit to receive uplink data in anuplink slot allocated to the station based on the information on the RAWor regularly allocated to the station at association, and a controllerto control the transmission unit to transmit an ACK with respect to theuplink data to the station and to control slot allocation, wherein theuplink slot includes a fixed size of slot duration.

A station of a wireless LAN system according to an exemplary embodimentincludes a reception unit to receive a beacon including a TIM bit froman AP and to receive an ACK including transmission slot allocationinformation on downlink data from the AP, a transmission unit totransmit a PS-Poll to the AP in a slot implicitly allocated by the TIMbit, and a controller to control a sleep mode and a wakeup mode based onslot allocation.

A station of a wireless LAN system according to another exemplaryembodiment includes a transmission unit to transmit uplink data to an APin an uplink slot, a reception unit to receive an ACK from the AP, and acontroller to control a sleep mode and a wakeup mode based oninformation on an RAW included in a beacon or information on a slotregularly allocated at association, wherein the uplink slot includes afixed size of slot duration.

Effects of Invention

According to exemplary embodiments, overhead in transmission slotallocation may be reduced and flexible slot allocation is enabled,thereby preventing waste of slot time and efficiently managingtransmission slots.

According to exemplary embodiments, waste of extra slot time may beavoided and time to wait for additional transmission of remaining datawhen transmission is not completed within a slot allocated to an STA maybe reduced.

Further, slot allocation information included in a beacon intransmission may be minimized and extra slots may be allowed for useunder control of the AP other than basically allocated slots.Accordingly, the extra slots may be optimally utilized and the STA doesnot need to wait for a next regular slot allocated to the STA totransmit the remaining data, thereby improving efficiency in use oftransmission slots.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates flexible transmission slot allocation in downlinktransmission in a wireless local area network (LAN) according to anexemplary embodiment.

FIG. 2 is a flowchart illustrating a flexible transmission slotallocation method of an AP in the wireless LAN system according to anexemplary embodiment.

FIG. 3 is a flowchart illustrating a flexible transmission slotallocation method of an STA in the wireless LAN system according to anexemplary embodiment.

FIG. 4 illustrates flexible transmission slot allocation in uplinktransmission in the wireless LAN system according to an exemplaryembodiment.

FIG. 5 illustrates a configuration of an access point (AP) in thewireless LAN system according to an exemplary embodiment.

FIG. 6 illustrates a configuration of a station (STA) in the wirelessLAN system according to an exemplary embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, exemplary embodiments of the present invention aredescribed in detail with reference to the accompanying drawings.

To use a slot-based channel access mode in a wireless local area network(LAN) system, transmission slot allocation is needed for stations.

Flexible transmission slot allocation disclosed in the specification mayhave six features as follows.

1. Stations (STAs) use regular slots initially allocated, and aretemporarily allocated additional slots upon request to an access point(AP) if needed. Thus, flexible slot allocation may be managed. Here, theSTAs may notify the AP of information on an uplink data size so as tohelp slot allocation and transmission scheduling of the AP.

2. In one restricted access window (RAW), slot duration has a fixedsize. Thus, slot allocation information included in the RAW may beminimized.

When slot durations are different within one RAW, start time andduration information for each slot duration are added, thus increasingslot allocation information. Here, when slot duration is insufficient,temporary slot allocation may be performed.

3. In downlink transmission, a slot for transmitting a power save poll(PS-Poll) is implicitly allocated according to bit order of a trafficindication map (TIM) of a beacon. When the AP transmits an ACK withrespect to the PS poll to the STAs, transmission slot allocationinformation on downlink data is included an acknowledgement (ACK)message.

4, In uplink transmission, an initial regular slot is allocated atassociation, and the STAs request allocation of temporary and additionalslots to the AP in addition to the allocated regular slot and areallocated temporary slots.

5. Even after association between the AP and the STAs, an operation modeof the STAs may be changed. Here, a change of the operation mode of theSTAs may be performed using an operating mode change request and anoperating mode change response. Further, the change of the operationmode may include an association identification (AID) change, an STAgroup change and a change of a sector that an STA belongs to.

6. Since slot allocation information on each STA is not necessarilyindicated in an RAW information element, slot allocation information maybe minimized. Here, the AP may notify an STA whether to allow additionalslots in the RAW.

FIG. 1 illustrates flexible transmission slot allocation in downlinktransmission in a wireless LAN according to an exemplary embodiment.

Referring to FIG. 1 , a dotted line denotes a slot boundary, DL denotesdownlink transmission, P denotes a PS-Poll transmitted by an STA to anAP, and A denotes an ACK frame.

Beacons 101 and 103 include a TIM bit. For example, an STA with the TIMbit set to 1 is implicitly allocated a PS-Poll transmission slot.Sequence of TIM bits may be set in the same order of AIDs allocated toSTAs.

First, an STA verifies a TIM bit included in a beacon for an STA groupthat the STA belongs to. The STA transmits a PS-Poll according tosequence of TIM bit setting. Thus, transmission of additionalinformation on transmission slot allocation is not needed.

The AP may indicate in the TIM bit that there is downlink data. Forexample, when the TIM bit is set to 1 for AIDs of 1, 5 and 7, STAshaving the AIDs of 1, 5 and 7 may recognize that a slot for transmittingthe PS-Poll is implicitly allocated.

For convenience of description, a terminal having an AID of 1 isreferred to as AID1, a terminal having an AID of 5 as AID5, and aterminal having an AID of 7 as AID7.

Referring to FIG. 1 , AID1 transmits a PS-Poll 111 and receives an ACK113 in a first slot boundary 110. Here, AID1 may recognize which slotAID1 is allowed to use to transmit the PS-Poll based on the set TIM bit.

STAs, that is, AID1, AID5 and AID7, may identify RAW start time and slotduration and determine an accurate time to transmit the PS-Poll byreferring to RAW information included in the beacon.

Like AID1, AID5 transmits a PS-Poll 121 and receives an ACK 123 in asecond slot boundary 120. Further, AID7 transmits a PS-Poll 131 andreceives an ACK 133 in a third slot boundary 130.

When there is currently pending uplink data, the STAs AID1, AID5 andAID7 may include information on a size of the uplink data in thePS-Poll. The AP may allocate slot duration of a next uplink RAW andslots for the STAs based on the information on the size of the uplinkdata.

Here, since slot duration in one RAW has the same fixed size,information on slot start time and slot duration by STA may not need tobe indicated separately.

In FIG. 1 , the ACK frames 113, 123 and 133 with respect to the PS-Pollinclude downlink slot allocation information on AID1, AID5 and AID7. TheAP already recognizes buffered data sizes for the respective STAs. Thus,the AP may insert slot allocation information, such as a downlink slotnumber, into the ACK frames.

In slot allocation, the AP may allow only a single slot to be allocatedfor one STA.

For example, the ACK frames may include a slot number only. Here, anormal ACK and a short ACK having a smaller frame size than the normalACK may be used.

When the slot number is transmitted through the short ACK, a limitednumber of slot numbers may be expressed. When a total number of slots isgreater than a reference level in one RAW, slot numbers may betransmitted using the normal ACK.

The AP may allocate a plurality of successive slots to one STA.

Here, the ACK frames may include not only slot numbers but a slot count.The AP may allocate a plurality of slots using the slot count.

For example, when an ACK frame is indicated with “3, 2,” slots 3 and 4are allocated. That is, “3, 2” indicated in the ACK frame may beinterpreted as allocation of two successive slots from the slot 3.

When the AP and the STAs agree to use a downlink RAW for transmission ofbuffered data immediately after the PS-Poll is transmitted, the slotnumbers or the slot numbers and slot count may be transmitted only.

However, when the downlink RAW is not used immediately after the PS-Pollis transmitted, not only the slot numbers or the slot numbers and slotcounter but also a downlink RAW number to use or RAW group informationmay be transmitted.

The STA may enter a sleep mode after receiving the ACK with respect tothe PS-Poll. The STA may wake up at a start point of an allocated slotand receive downlink data.

Referring to FIG. 1 , AID1 may receive downlink data in a downlink datatransmission section 141 of a fourth slot boundary 140 and transmit anACK 143 to the AP.

AID5 may receive downlink data in a downlink data transmission section151 of a fifth slot boundary 150 and transmit an ACK 153 to the AP.

AID7 may receive downlink data in a downlink data transmission section161 of a fourth slot boundary 160 and transmit an ACK 163 to the AP.

The AP may allocate an additional slot for downlink data transmission.

The AP may indicate in the downlink data that there is additionaldownlink data. For example, the AP may include a “More data (MD) bit” inthe downlink data and set the More data bit to 0 or 1. Here, a More databit of 1 indicates that there is more data to transmit.

In FIG. 1 , AID1 and AID7 receive data with an MD bit set to 0, whileAID5 has an MD bit set to 1.

Here, AID1 and AID7 determine that there is no more data to receivebased on the MD bit, and may enter the sleep mode immediately aftertransmitting the ACKs 143 and 164. AID5 needs to additionally receivebuffered data.

AID5 may receive additional downlink data in a downlink datatransmission section 171 of a seventh slot boundary 170 and transmit anACK 173 to the AP.

When the MD bit is 1 and it is impossible to transmit remaining data tothe STA within a currently allocated slot, the AP may allocate an extraslot to the STA. For example, AID5 has an MD bit of 1 and cannot receiveremaining data within a currently allocated slot in the fifth slotboundary.

Here, when there are remaining slots and thus allocation of anadditional slot is possible, the AP may notify the STA of information ona slot to be additionally allocated. For example, the information on theslot to be additionally allocated may include at least one of anadditional RAW number, an RAW group and a slot number. Here, when anextra slot in the same RAW is additionally allocated, the AP maytransmit only a number of the slot to be additionally allocated. The APmay aggregate the information on the slot to be additionally allocatedwith a data frame transmitted to the STA in transmission. For example,the slot allocation information may be included in an MAC header or SIGfield of the data frame sent by the AP and transmitted.

For example, AID5 includes information on an additional slot allocatedby the AP in a data frame received within the fifth slot boundary.

The STA may notify the AP whether to receive additional data in the slotadditionally allocated by the AP or in a next delivery trafficindication map (DTIM) when transmitting the ACK frame.

When the STA does not receive the additional data in the additionallyallocated slot, the STA may wake up, transmit the PS-Poll and receivethe additional data in the next DTIM.

In FIG. 1 , the downlink transmission section 171 in the seventh slotboundary 170 is a temporary slot additionally allocated.

When the MD bit is 1, it is impossible to transmit remaining data withina currently allocated slot to the STA and there is no extra slot, the APmay transmit information reporting that no more data can be transmittedin the allocated slot to be aggregated with the data frame. Here, theSTA enters the sleep mode, and then wakes up, transmits the PS-Poll tothe AP and receives data in a next DTIM that the STA belongs to.

FIG. 2 is a flowchart illustrating a flexible transmission slotallocation method of an AP in the wireless LAN system according to anexemplary embodiment.

Referring to FIG. 2 , the AP transmits a beacon including a TIM bit toan STA in operation 210.

Here, the TIM bit may indicate transmission order of PS-Polls andinformation on existence of downlink data. Further, the beacon includesinformation on a RAW, the information on the RAW includes start time ofthe RAW and slot duration, and the slot duration has a fixed size.

Here, before operation 210, initial slot allocation may be carried out.The AP may receive an association request from the STA and transmit anassociation response including an AID to the STA.

Here, the STA may transmit information relevant to STA grouping, forexample, a device type, power save parameters including a listeninterval, a maximum idle period, a wireless network management (WNM)sleep interval and a wakeup interval, a TIM/non-TIM operation mode, atraffic type, a service type and a sector that the STA belongs to, tothe AP via the association request at association with the AP. The APallocates an AID to the STA and groups the STA into a particular groupbased on the information.

The AP may transmit allowed power save parameters including an listeninterval, a maximum idle period, a WNM-sleep interval and a wakeupinterval, the AID allocated to the STA, the STA group and an initialuplink slot number to the STA in the association response.

When the STA group is implicitly allocated based on the AID allocated bythe AP and uplink slot allocation information is transmitted through thebeacon, the STA group and the initial uplink slot number may not needtransmitting in the association response.

The STA group and the slot number may be identified only with the AID.When the uplink slot allocation information is not transmitted throughthe beacon, an initial uplink slot may be allocated at association.

Generally, an STA is allocated one AID, and the AP may allocate one STAfor a plurality of RAWs. For example, the AP may allocate the STA for aplurality of RAWs, such as an uplink RAW and an up/downlink RAW.

When the STA supports two or more device types, the STA may be allocatedAIDs for the respective device types, belong to separate STA groups byAIDs and be allocated for separate RAWs by AIDs.

Further, when the STA switches between TIM/non-TIM modes, the STA may beallocated an AID for a TIM operation and a separate AID for a non-TIMoperation and allocated separate STA groups and separate RAWs.

In downlink transmission, a slot used for transmitting the PS-Poll isimplicitly allocated according to TIM bit sequence of the beacon, anddownlink data transmission slot allocation information may betransmitted in an ACK to the STA when the AP transmits the ACK withrespect to the PS-Poll.

Meanwhile, when AID reallocation is carried out, the AP may reallocate aslot within the RAW allowed for the STA group that the STA belongs to.

The STA may request a change of an operation mode of the STA, such as anAID change, an STA group change and a sector change, using an operatingmode change request and response even after association.

The AP may control the change of the operation mode of the STA. Ifnecessary, the AP may change the operation mode without a request fromthe STA. For example, the AP may notify the STA of an AID change, an STAgroup change, a change of sector allocation for the STA and a slotallocation change.

When an operating mode change is requested, an AID may be reallocated.Here, the STA group may be changed, and the AP reallocates a slot withinthe RAW allowed for the STA group.

In operation 220, the AP receives a PS-Poll from the STA in a slotimplicitly allocated by the TIM bit. For example, the AP may receive thePS-Poll in the slot 111 transmitted from AID1 of FIG. 1 .

In operation 230, the AP transmits an ACK including transmission slotallocation information on downlink data to the STA.

As shown in FIG. 1 , the AP may transmit the downlink data to the STA inthe allocated downlink data transmission slot after operation 230. Here,the downlink data may include temporary slot allocation information onadditional downlink data.

FIG. 3 is a flowchart illustrating a flexible transmission slotallocation method of an STA in the wireless LAN system according to anexemplary embodiment.

Referring to FIG. 3 , the STA receives a beacon including a TIM bit fromthe AP in operation 310.

The STA may determine the sleep mode or a wakeup mode based ontransmission order of PS-Polls and information about existence ofdownlink data.

Here, a PS-Poll includes information on a size of pending uplink data ofthe STA, and the STA may be allocated a slot of a next uplink RAW basedon the size.

In operation 320, the STA transmits a PS-Poll to the AP in a slotimplicitly allocated by the TIM bit.

In operation 330, the STA receives an ACK including transmission slotallocation information on downlink data from the AP.

After operation 330, the STA may receive ‘downlink data includingadditionally allocated slot information’ in the allocated downlink datatransmission slot and transmit an ACK with respect to the downlink datato the AP. Here, the ACK may include information on whether to use theadditionally allocated slot or to wake up in a next DTIM.

FIG. 4 illustrates flexible transmission slot allocation in uplinktransmission in the wireless LAN system according to an exemplaryembodiment.

Uplink transmission may includes the following processes (a) to (c).

(a) The AP transmits a beacon including information on an RAW to an STA.The STA verifies the information on the RAW included in the beacons 401and 403 or information on a slot regularly allocated at association.

(b) The STA transmits uplink data to the AP in an uplink slot. The APreceives the uplink data in the uplink slot allocated to the STA basedon the information on the RAW or regularly allocated to the STA atassociation.

The uplink data may include information on whether there is extra datain addition to the data transmitted through the uplink slot, forexample, an MD bit.

(c) The AP transmits an ACK with respect to the uplink data to the STA.The STA receives the ACK from the AP. Here, slot duration of the uplinkslot has a fixed size. Here, the ACK includes information on additionalslot allocation for the additional data, and the STA may determine thesleep mode and the wakeup mode based on the information on theadditional slot allocation.

Referring to FIG. 4 , a dotted line denotes a slot boundary, UL denotesuplink transmission, and A denotes an ACK frame.

For convenience of description, a terminal having an AID of 1 isreferred to as AID1, a terminal having an AID of 3 as AID3, and aterminal having an AID of 7 as AID7.

The information on the RAW may be included in GrPS of the beacon 401.The STA may identify which slot the STA is allocated through theinformation on the RAW. When an allocated fixed slot is used in initialslot allocation, the information on the RAW may not be needed.

When one STA is allocated only a single slot within one RAW, slotduration is the same, and thus the STA may not receive additional slotallocation map information.

When one STA is allocated a plurality of successive slots within oneRAW, the information on the RAW may include not only slot numbers but aslot count.

For example, when the information on the RAW is indicated with “4, 2,”slots 4 and 5 are allocated. That is, “4, 2” indicated in the RAW may beinterpreted as allocation of two successive slots from the slot 4.

The STA may wake up at start time of the allocated slot and transmit theuplink data.

Referring to FIG. 4 , AID1 may wake up and transmit uplink data in anuplink data transmission section 411 of a slot boundary 410 and receivean ACK 413.

AID3 may transmit uplink data in an uplink data transmission section 421of a slot boundary 420 and receive an ACK 423.

AID7 may transmit uplink data in an uplink data transmission section 431of a slot boundary 430 and receive an ACK 433.

To further provide slot allocation flexibility, an additional ortemporary slot may be allocated when the regularly allocated slot isinsufficient for uplink data transmission.

The STA may indicate in an MAC header that there is more data totransmit when it is impossible to completely transmit pending datawithin the regularly allocated slot in uplink data transmission.

For example, in FIG. 4 , AID1 and AID3 may set the More Data bit to 1 tonotify the AP that there is additional data to transmit.

The STA may set the MD bit to 1 only when it is impossible to completelytransmit pending data within the regularly allocated slot, or set the MDbit to 1 regardless of remaining slot time when there is pending data touplink-transmit.

When the MD bit is set to 1 only when it is impossible to completelytransmit pending data within the regularly allocated slot, the STA maynotify the AP that it is impossible to complete transmission of pendingdata within the regularly allocated slot.

When the MD bit is to 1 regardless of remaining slot time when there ispending data to uplink-transmit, the STA may need to use additionalinformation to notify the AP that it is impossible to completetransmission of pending data within the regularly allocated slot. Forexample, the STA may transmit 1-bit “additional slot necessary” alongwith the MD bit set to 1.

Even though the STA does not completely transmit the data, when the STAwishes to wake up and transmit remaining data in a next regular slotallocated to the STA without allocation of additional or temporaryslots, the STA may transmit an additional slot necessary bit set to 0and enter the sleep mode after receiving an ACK from the AP.

The STA may notify the AP of a remaining uplink data size along withmore data information in uplink data transmission. For example, the STAmay notify the AP of information on the uplink data size by aggregatinginformation on the remaining uplink data size with the MAC header orusing an SIG field. The AP may use the information on the uplink datasize for additional temporary slot allocation.

When the AP is able to temporarily allocate an extra uplink slot to theSTA, the AP may allocate the extra slot and notify the STA ofinformation on the allocated slot to be included in an ACK. Here, theinformation on the allocated slot may include an RAW number, RAW groupinformation and a slot number.

In FIG. 4 , AID1 and AID3 transmit data with the MD bit set to 1, whileAID7 has the MD bit set to 0. Here, AID7 may enter the sleep modeimmediately after receiving the ACK 433.

AID1 may transmit additional data in an uplink data transmission section441 of a slot boundary 440 and receive an ACK 443 from the AP. Further,AID3 may transmit additional data in an uplink data transmission section451 of a slot boundary 450 and receive an ACK 453.

Here, only when additional temporary RAW allocation is allowed for theRAW, a slot of the RAW may be additionally allocated. Allowance oftemporary RAW allocation may be indicated in GrPS of the RAW.

When an extra slot in the same RAW is allocated, the AP may transmit aslot number only. The additional slot allocation information may beaggregated with an ACK frame transmitted by the AP to the STA andtransmitted. For example, the slot allocation information may beincluded in the MAC Header or SIG field. When the slot allocationinformation is short, the slot allocation information may be included ina short ACK and transmitted. When the slot allocation information islonger than a reference level, the slot allocation information may beincluded in a normal ACK and transmitted.

When additional slot allocation is not allowed or there is no extraslot, the STA transmits the remaining uplink data in a next regular slotallocated to the STA.

When the AP is unable to allocate an additional slot to the STA, the APmay transmit information reporting that no more data can be transmittedin the allocated slot to be aggregated with the ACK. Here, the STAenters the sleep mode, and then wakes up and transmits the remaininguplink data in the next regular slot allocated to the STA.

FIG. 5 illustrates a configuration of an AP in the wireless LAN systemaccording to an exemplary embodiment.

Referring to FIG. 5 , the AP 500 includes a transmission unit 510, areception unit 520 and a controller 530.

The transmission unit 510 transmits a beacon including a TIM bit to anSTA. Further, the transmission unit 510 transmits a beacon includinginformation on an RAW to the STA.

The reception unit 520 receives a PS-Poll from the STA in a slotimplicitly allocated by the TIM bit. Further, reception unit 520receives uplink data in an uplink slot allocated to the STA based on theinformation on the RAW or regularly allocated to the STA at association.

The controller 530 may control the transmission unit to transmit an ACKincluding transmission slot allocation information on downlink data tothe STA and control slot allocation. Further, the controller 530 maycontrol the transmission unit to transmit an ACK with respect to uplinkdata to the STA and control slot allocation.

FIG. 6 illustrates a configuration of an STA in the wireless LAN systemaccording to an exemplary embodiment.

Referring to FIG. 6 , the STA 600 includes a reception unit 610, atransmission unit 620 and a controller 630.

The reception unit 610 receives a beacon including a TIM bit from the APand receives an ACK comprising transmission slot allocation informationon downlink data from the AP.

Further, the reception unit 610 receives an ACK with respect to uplinkdata from the AP.

The transmission unit 620 transmits a PS-Poll to the AP in a slotimplicitly allocated by the TIM bit. Also, the transmission unit 620transmits the uplink data to the AP in an uplink slot.

The controller 630 controls the sleep mode and the wakeup mode of theSTA 600 based on slot allocation. Further, the controller 630 controlsthe sleep mode and the wakeup mode of the STA 600 based on informationon an RAW included in the beacon or information on a slot regularlyallocated at association.

The methods according to the exemplary embodiments may be recorded incomputer-readable media as program instructions to be implemented byvarious computers. The media may also include, alone or in combination,the program instructions, data files, data structures, and the like. Themedia and program instructions may be those specially designed andconstructed for the purposes of the present invention, or they may be ofthe kind well-known and available to those having skill in the computersoftware arts. Examples of computer-readable media include magneticmedia such as hard disks, floppy discs and magnetic tape; optical mediasuch as CD ROM discs and DVDs; magneto-optical media such as flopticaldiscs; and hardware devices that are specially configured to store andperform program instructions, such as read-only memory (ROM), randomaccess memory (RAM), flash memory, and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and higher level code that may be executed by a computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described exemplary embodiments, or vice versa.

While a few exemplary embodiments have been shown and described withreference to the accompanying drawings, it will be apparent to thoseskilled in the art that various modifications and variations can be madefrom the foregoing descriptions. For example, adequate effects may beachieved even if the foregoing processes and methods are carried out indifferent order than described above, and/or the aforementionedelements, such as systems, structures, devices, or circuits, arecombined or coupled in different forms and modes than as described aboveor be substituted or switched with other components or equivalents.

Thus, other implementations, alternative embodiments and equivalents tothe claimed subject matter are construed as being within the appendedclaims.

The invention claimed is:
 1. A method of uplink transmission by astation (STA) in a wireless local area network, the method comprising:receiving, from an access point (AP), an uplink soliciting frameincluding information on a plurality of an association identifier (AID)and information on resource allocation based on the AID, wherein eachSTA has its own AID and information on resource allocation includesinformation of each STA's resource allocation based on AID; wherein theuplink soliciting frame is transmitted by the AP without a request fromthe STA, and the uplink soliciting frame solicits the STA to report anamount of uplink data buffered at the STA, wherein the informationindicating an amount of uplink data buffered at the STA is included inmedium access control (MAC) header of the frame transmitted to the AP;in response to the uplink soliciting frame, transmitting, through anallocated resource based on the resource allocation included in theuplink soliciting frame, a first uplink transmission frame including theinformation indicating an amount of uplink data buffered at the STA whenthe transmission for the remaining data of the STA is impossible basedon the allocated resource; receiving a data soliciting frame includinginformation on the data transmission resource for the next transmissionof the STA based on the information indicating an amount of uplink databuffered at the STA; and transmitting, using the data transmissionresource indicated by the data soliciting frame for the nexttransmission of the STA, a second uplink transmission frame includingdata to the AP.
 2. The method of claim 1, wherein the first uplinktransmission frame includes data and information indicating the amountof uplink data buffered at the STA based on the AID to assist the AP inallocating a data transmission resource for the next transmission of theSTA.
 3. A method of uplink reception by an access point (AP) in awireless local area network, the method comprising: transmitting, to astation (STA), an uplink soliciting frame including information on aplurality of an association identifier (AID) and information on resourceallocation based on the AID, wherein each STA has its own AID andinformation on resource allocation includes information of each STA'sresource allocation based on AID; wherein the uplink soliciting frame istransmitted by the AP without a request from the STA and the uplinksoliciting frame solicits the STA to report an amount of uplink databuffered at the STA, wherein the information indicating an amount ofuplink data buffered at the STA is included in medium access control(MAC) header of the frame transmitted to the AP; in response to theuplink soliciting frame, receiving, through an allocated resource basedon the resource allocation included in the uplink soliciting frame, afirst uplink transmission frame including the information indicating anamount of uplink data buffered at the STA when the transmission for theremaining data of the STA is impossible based on the allocated resource;transmitting a data soliciting frame including information on the datatransmission resource for the next transmission of the STA based on theinformation indicating an amount of uplink data buffered at the STA; andreceiving, using the data transmission resource indicated by the datasoliciting frame for the next transmission of the STA, a second uplinktransmission frame including data from the STA.
 4. The method of claim3, wherein the first uplink transmission frame includes data andinformation indicating the amount of uplink data buffered at the STAbased on the AID to assist the AP in allocating a data transmissionresource for the next transmission of the STA.
 5. An apparatus of astation (STA) performing uplink transmission in a wireless local areanetwork, the apparatus comprising: a receiver; a transmitter; and acontroller, wherein the controller is configured to: receive, using thereceiver, from an access point (AP), an uplink soliciting frameincluding information on a plurality of an association identifier (AID)and information on resource allocation based on the AID, wherein eachSTA has its own AID and information on resource allocation includesinformation of each STA's resource allocation based on AID, wherein theuplink soliciting frame is transmitted by the AP without a request fromthe STA, and the uplink soliciting frame solicits the STA to report anamount of uplink data buffered at the STA, wherein the informationindicating an amount of uplink data buffered at the STA is included inmedium access control (MAC) header of the frame transmitted to the AP,in response to the uplink soliciting frame, transmit, using thetransmitter, through an allocated resource based on the resourceallocation included in the uplink soliciting frame, a first uplinktransmission frame including the information indicating an amount ofuplink data buffered at the STA when the transmission for the remainingdata of the STA is impossible based on the allocated resource, receive adata soliciting frame including information on the data transmissionresource for the next transmission of the STA based on the informationindicating an amount of uplink data buffered at the STA, and transmit,using the data transmission resource for the of transmission from theSTA, a second uplink transmission frame including data to the AP.
 6. Themethod of claim 5, wherein the first uplink transmission frame includesdata and information indicating the amount of uplink data buffered atthe STA based on the AID to assist the AP in allocating a datatransmission resource for the next transmission of the STA.
 7. Anapparatus of an access point (AP) performing uplink reception in awireless local area network, the apparatus comprising: a receiver; atransmitter; and a controller, wherein the controller is configured to:transmit, using the transmitter, to a station (STA), an uplinksoliciting frame including information on a plurality of an associationidentifier (AID) and information on resource allocation based on theAID, wherein each STA has its own AID and information on resourceallocation includes information of each STA's resource allocation basedon AID, wherein the uplink soliciting frame is transmitted by the APwithout a request from the STA and the uplink soliciting frame solicitsthe STA to report an amount of uplink data buffered at the STA, whereinthe information indicating an amount of uplink data buffered at the STAis included in medium access control (MAC) header of the frametransmitted to the AP, in response to the uplink soliciting frame,receive, using the receiver, through an allocated resource based on theresource allocation included in the uplink soliciting frame, a firstuplink transmission frame including the information indicating an amountof uplink data buffered at the STA when the transmission for theremaining data of the STA is impossible based on the allocated resource,transmit a data soliciting frame including information on the datatransmission resource for the next transmission of the STA based on theinformation indicating an amount of uplink data buffered at the STA, andreceive, using the data transmission resource for the next transmissionof the STA, a second uplink transmission frame including data from theSTA.
 8. The method of claim 7, wherein the first uplink transmissionframe includes data and information indicating the amount of uplink databuffered at the STA based on the AID to assist the AP in allocating adata transmission resource for the next transmission of the STA.